The present disclosure relates to the subject matter contained in Japanese Utility Model Application No. U2002-000337 filed Jan. 29, 2002, which is incorporated herein by reference in its entirety.
1. Field of the Invention
This invention relates to a rotational driving apparatus of a magnetic tape device, particularly to a rotational driving apparatus capable of rapidly forwarding and rewinding a magnetic tape.
2. Description of the Related Art
Fast forwarding and rewinding of a magnetic tape device are carried out frequently, such as when finishing a reproduction, or when selecting images. In order to carry out such the fast forwarding and rewinding of a magnetic tape, it is necessary that the magnetic tape be made to run at a speed higher than a normal level.
It is conceivable to set a reduction ratio in a rotation transmission path extending from a motor to a reel low so as to increase a rotational speed of the reel. However, if the reduction ratio is set too low, the motor need to be rotated at a very low speed during a normal reproduction operation. As a result, the rotational stability of the reel during the reproduction operation is deteriorated. This may cause a disarrangement of a reproduced picture image or a deterioration of the quality of a reproduced picture image.
A magnetic tape device capable of carrying out rapid forwarding and rewinding of a magnetic tape is provided with a mechanism for transmitting a motor rotation to a reel through a transmission path different from that used during a reproduction operation, just as disclosed in, for example, JP-A-5-274749.
In a magnetic tape device provided with a rotation transmission path different from that used during a reproduction operation so as to enable a rapid forwarding and rewinding of a magnetic tape to be carried out, the number of parts increases by constructing the additional rotation transmission path, and the universality of the magnetic tape device is lost due to the special construction. Also, there may be some cases where a space in which parts necessary for carrying out the rapid forwarding and rewinding of a magnetic tape are installed need to be provided. Such a magnetic tape device goes against a space saving concept.
An object of the present invention is to provide a rotational driving apparatus of a magnetic tape device capable of carrying out rapid forwarding and rewinding of a magnetic tape without specially changing the construction thereof and without causing the quality of a reproduced picture image to be deteriorated.
According to a first aspect of the invention, there is provided a rotational driving apparatus of a magnetic tape device adapted to transmit a rotation of a motor to a clutch mechanism, and transmit the rotation of the clutch mechanism to a feed reel or a take-up reel selectively via a rotation transmission path change-over gear. A first clutch mechanism and a second clutch mechanism can be provided selectively as the clutch mechanism. The first clutch mechanism being adapted to decelerate the rotation of the motor at a first reduction gear ratio, and transmit the resultant rotation to the change-over gear. The first clutch mechanism has a first shaft, a first pulley, a first clutch output gear, a first constant torque transmission member and a clutch member. The first pulley is adapted to receive the rotation of the motor and supported rotatably on the first shaft. The first clutch output gear is meshed with the change-over gear supported rotatably on the first shaft. The first constant torque transmission member is provided between the first pulley and first clutch output gear and adapted to transmit torque of lower than a predetermined level from the second pulley thereto. The clutch member is adapted to transmit the rotation of the first pulley to the first clutch output gear via the first constant torque transmission member or directly. On the other hand, the second clutch mechanism is adapted to decelerate the rotation of the motor at a second reduction ratio and transmit the resultant rotation to the change-over gear. The second clutch mechanism has a second shaft, a second pulley, a second clutch output gear, a second constant torque transmission member and a speed change clutch member. The second pulley is supported rotatably on the second shaft. The second clutch output gear is meshed with the change-over gear supported rotatably on the second shaft. The second constant torque transmission member is provided between the second pulley and second output gear and adapted to transmit torque of lower than a predetermined level from the second pulley thereto. The speed change clutch member is provided close to the second shaft and adapted to transmit the rotation of the second pulley to the second clutch output gear via the second constant torque transmission member or directly with the speed of the rotation changed.
In this rotational driving apparatus of a magnetic tape device, the first clutch mechanism and second clutch mechanism can be provided selectively as the clutch mechanism for the rotation transmission path. In the second clutch mechanism, which is different from the first clutch mechanism, the transmission of the rotation of the motor can be carried out with the speed of the rotation changed. Namely, when the speed of the rotation of the motor is changed by the second clutch mechanism at the time of, for example, carrying out rapid forwarding and rewinding of a magnetic tape, these magnetic tape handling operations can be executed at a high speed as compared with the same operations in a case where the first clutch mechanism is used. Conversely, since the speed of the rotation is changed at the time of carrying out rapid forwarding and rewinding of the magnetic tape, the reel can be rotated stably at a low speed at the time of the reproduction. Moreover, this rotational driving apparatus of a magnetic tape device is capable of using structures, other than the clutch mechanism, in common. Therefore, this rotational driving apparatus of a magnetic tape device is capable of improving a mass production efficiency thereof, and manufacturing the apparatus at a low cost.
According to a second aspect of the invention, the clutch member of the first clutch mechanism is supported on the first shaft axially movably so that the clutch member can be rotated with respect to the first shaft and engaged with and disengaged from the first pulley, the clutch member in a first pulley-disengaged state transmits the rotation of the first pulley to the first clutch output gear via the first constant torque transmission member, the clutch member in a first pulley-engaged state transmits the rotation of the first pulley to the clutch output gear directly.
In this apparatus, the clutch member is engageable with and disengageable from the first pulley. When the clutch member is disengaged from the first pulley, the rotation of the first pulley is transmitted to the first clutch output gear by the first constant torque transmission member, so that only the torque of lower than a predetermined level is transmitted. Therefore, when a sudden torque is transmitted from the motor, the transmission of the torque to the first clutch output gear can be prevented. This enables the possibility that a sudden tension, which causes the magnetic tape to be broken in some cases, be imparted to the magnetic tape to be eliminated. On the other hand, when the clutch member is engaged with the first pulley at the time of carrying out rapid forwarding and rewinding of the magnetic tape, the rotation of the motor can be wholly transmitted.
According to a third aspect of the invention, the second pulley of the second clutch mechanism has a gear portion at an outer circumferential section thereof. The second clutch mechanism has a transmission gear to which the rotation of the second pulley is transmitted via the second constant torque transmission member. The speed change clutch member of the second clutch mechanism has a speed change support shaft, a speed change intermediate gear and a clutch. The speed change support shaft is provided in parallel with the second shaft. The speed change intermediate gear is supported rotatably on the speed change support shaft and meshed with the gear portion of the second pulley. The clutch is supported on the speed change support shaft rotatably and axially movably so that the clutch can be engaged with and disengaged from the speed change intermediate gear. The clutch has a first gear portion meshable with the transmission gear, and a second gear portion meshable with the second clutch output gear. The clutch is adapted to change in a speed change intermediate gear-disengaged state a speed of the rotation from the transmission gear via the first gear portion and second gear portion, and transmit the resultant rotation to the second clutch output gear; and transmit in a speed change intermediate gear-engaged state the rotation of the speed change intermediate gear to the second clutch output gear via the second gear portion. The number of the teeth of the first gear portion and that of the teeth of the second gear portion are equal to each other and larger than that of the teeth of the speed change intermediate gear. The number of the teeth of the transmission gear and that of the teeth of the second clutch output gear are equal to each other and smaller than that of the teeth of the gear portion of the second pulley.
In this apparatus, the clutch can be engaged with and disengaged from the speed change intermediate gear. When the clutch is disengaged from the speed change intermediate gear, the rotation of the second pulley can be output to the second clutch output gear. Since the rotation of the second pulley is transmitted to the second clutch output gear by the second constant torque transmission member, only the torque lower than a predetermined level is transmitted. Therefore, when a sudden torque is transmitted from the motor, the transmission of the torque to the second clutch output gear can be avoided. As a result, the possibility that a sudden tension, which causes the magnetic tape to be broken, be imparted to the magnetic tape can be eliminated. As a transmission path, a path in which the rotation of the motor is transmitted to the change-over gear via the second pulley, second constant torque transmission member, clutch (first gear portion and second gear portion) and second clutch output gear may be used.
When the clutch is engaged with the speed change intermediate gear at the time of carrying out rapid forwarding and rewinding of a magnetic tape, the rotation of the motor can be wholly transmitted. Since during this time a speed of the rotation of the second pulley is changed with the resultant rotation transmitted to the second clutch output gear, rapid forwarding and rewinding of the magnetic tape can be achieved. As a transmission path, a path in which the rotation of the motor is transmitted to the change-over gear via the second pulley, speed change intermediate gear, clutch (second gear portion) and second clutch output gear maybe used. Therefore, the reduction ratio is different due to a difference in the number of teeth in the transmission path as compared with a reduction ratio in a case where the clutch is not engaged with the speed change intermediate gear, so that it follows that a speed change is certainly made.
As described above, a reduction ratio employed when the reel is rotated at a low speed at the time of reproducing or the like, and a reduction ratio employed when the reel is rotated at a high speed at the time of carrying out rapid forwarding and rewinding of the magnetic tape can be set to different levels. Therefore, rotating the reel stably at a low speed and rotating the reel at a high speed can be done compatibly.
According to a fourth aspect of the invention, a rotational driving apparatus of a magnetic tape device is formed so as to transmit a rotation of a motor to a clutch mechanism, and the rotation of the clutch mechanism to a feed reel or a take-up reel selectively via a rotation transmission path change-over gear. The clutch mechanism includes a first shaft, a pulley, a transmission gear, a constant torque transmission member, a speed change output gear, a second shaft, a speed change intermediate gear and a clutch. The pulley is supported rotatably on the first shaft, has a gear portion at an outer circumferential section thereof and is adapted to receive the rotation transmitted from the motor. The transmission gear is supported rotatably on the first shaft. The constant torque transmission member is adapted to transmit torque of lower than a predetermined level from the pulley to the transmission gear. The speed change output gear is supported rotatably on the first shaft and meshed with the change-over gear. The second shaft is provided in parallel with the first shaft. The speed change intermediate gear is supported rotatably on the second shaft and meshed with the gear portion of the pulley. The clutch has a first gear portion meshable with the transmission gear, and a second gear portion supported movably and rotatably on the second shaft and meshable with a speed change output gear. The clutch can take a first position in which the clutch is disengaged from the speed change intermediate gear and transmits the rotation of the transmission gear to the speed change output gear via the first gear portion and second gear portion, and a second position in which the clutch is engaged with the speed change intermediate gear and transmits the rotation of the speed change intermediate gear to the speed change output gear via the second gear portion.
In this apparatus, the clutch can be engaged with and disengaged from the speed change intermediate gear. When the clutch is disengaged from the speed change intermediate gear, i.e., in the first position, the rotation of the pulley can be output to the clutch output gear by the constant torque transmission member. Since the constant torque transmission member transmits the rotation of the pulley to the clutch output gear, only torque of lower than a predetermined level is transmitted. Therefore, the possibility that a sudden tension, which causes the magnetic tape to be broken, be imparted to the magnetic tape is thereby eliminated. As a transmission path, path in which the rotation of the motor is transmitted to the change-over gear via the pulley, constant torque transmission member, transmission gear, clutch (first gear portion and second gear portion) and clutch output gear may be used.
When rapid forwarding and rewinding of the magnetic tape are carried out, the clutch is engaged with the speed change intermediate gear. When the clutch is in the second position, the rotation of the motor can be wholly transmitted. At this time, the rotation of the pulley is transmitted to the clutch output gear by changing the speed thereof, so that the forwarding and rewinding of the magnetic tape can be done at a high speed. As a transmission path, a path in which the rotation of the motor is transmitted to the change-over gear via the pulley, speed change intermediate gear, clutch (second gear portion) and clutch output gear may be used. Therefore, the reduction ratio is different from that employed in a case where the clutch is not engaged with the speed change intermediate gear due to a difference between the number of the teeth in the transmission paths in these cases, so that it follows that a speed change is certainly made.
As described above, a reduction ratio employed when the reel is rotated at a low speed at the time of reproducing or the like, and a reduction ratio employed when the reel is rotated at a high speed at the time of carrying out rapid forwarding and rewinding, etc. of the magnetic tape can be set to different levels. Therefore, rotating the reel stably at a low speed and rotating the reel at a high speed can be done compatibly.
Since the structure of the clutch mechanism is simple, it becomes possible to manufacture a rotational driving apparatus at a low cost.